JP2010117526A - Ultraviolet irradiation apparatus, and coating formation method of optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet irradiation apparatus having a longer lifetime, a smaller power consumption and lower running cost in comparison with an ultraviolet irradiation apparatus using a UV lamp, and to provide a coating formation method of an optical fiber. <P>SOLUTION: In this ultraviolet irradiation apparatus wherein coating layers C1, C2 comprising an ultraviolet curing resin are applied onto the surface of the optical fiber F1, and the ultraviolet curing resin is cured by irradiating an ultraviolet ray thereto, at least two or more semiconductor light emitting elements 34 provided on a position where the ultraviolet ray is irradiated are included in the ultraviolet curing resin, and first and second semiconductor light emitting elements emit ultraviolet rays having each different peak wavelength. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultraviolet irradiation apparatus for curing a resin applied on the surface of an optical fiber and a method for forming a coating on the optical fiber.

Conventionally, a resin coating is applied to the surface of a bare optical fiber drawn from a preform or an optical fiber strand once wound on a bobbin. The outer periphery of the optical fiber is covered with an ultraviolet curable resin (UV light curable resin), and the UV light curable resin is cured by irradiating the UV light curable resin with ultraviolet light (UV light). Patent Document 1 below uses one or a plurality of ultraviolet semiconductor light-emitting elements such as an ultraviolet laser diode (UV-LD) or an ultraviolet light-emitting diode (UV-LED) as a light source of UV light to achieve reduction of power consumption. I am trying.
JP 2003-89555 A

  However, as a result of intensive studies by the inventors of the present application, it has been found that the above-described conventional apparatus has insufficient curing of the coating covering the optical fiber, which adversely affects the quality of the optical fiber.

  That is, the UV-LED has a single, narrow (about ± 5 nm) emission spectrum, and the wavelength (peak wavelength) that gives the peak value of this emission spectrum is the light contained in the UV photocurable resin. It may not exist in the vicinity of the wavelength that gives the peak value or shoulder value of the absorption spectrum of the polymerization initiator. In that case, there is a problem that radical generation from the photopolymerization initiator is suppressed and the resin curing reaction is not accelerated. From this point of view, it is considered that the UV lamp is more effective for sufficiently promoting the resin curing. However, the UV lamp has a drawback that it has a short life and high power consumption.

  The present invention has been made in view of the above-mentioned problems, and has a long life, low power consumption, and low running cost compared to an ultraviolet irradiation apparatus using a UV lamp, and coating formation of an optical fiber. It aims to provide a method.

  In order to solve the above-mentioned problems, an ultraviolet irradiation apparatus according to the present invention is an ultraviolet irradiation apparatus in which an ultraviolet curable resin applied to the surface of an optical fiber is irradiated with ultraviolet rays to cure the ultraviolet curable resin. The mold resin is provided with at least first and second semiconductor light emitting elements provided at positions where ultraviolet rays can be irradiated, and the first and second semiconductor light emitting elements emit ultraviolet rays, and their peak wavelengths are different. .

  According to the apparatus of the present invention, since it has at least two spectral peaks in the ultraviolet band, curing of the ultraviolet curable resin can be sufficiently promoted. The ultraviolet band is a wavelength range of 10 nm to 400 nm. As a result, the semiconductor light-emitting element has a longer lifetime and lower power consumption than the UV lamp, and therefore has a lower running cost. Therefore, the apparatus of the present invention can sufficiently accelerate the curing of the ultraviolet curable resin in spite of the use of the semiconductor light emitting element, so that it can operate with a long life, low power consumption, and low running cost. It becomes possible.

  Moreover, it is preferable that the first and second semiconductor light emitting elements are arranged so as not to emit ultraviolet rays toward the light emitting surface of a semiconductor light emitting element other than itself. When ultraviolet light from another semiconductor light emitting element is incident on the light emitting surface of the semiconductor light emitting element, oscillation or the like occurs inside, and the temperature of the semiconductor light emitting element deteriorates, and the life of the semiconductor light emitting element deteriorates. Then, the first and second semiconductor light emitting elements are arranged so as to avoid such a state. Therefore, the life of the semiconductor light emitting device can be extended.

  The first and second semiconductor light emitting elements are preferably thermally connected to a water cooling device. Preferably, the first and second semiconductor light emitting elements are cooled by bringing a water cooling device into contact with a base on which the semiconductor light emitting elements are fixed. The cooling water removes heat from the semiconductor light emitting element, and the semiconductor light emitting element can be maintained at a relatively low constant temperature, so that the life of the semiconductor light emitting element can be extended. In addition, since the semiconductor light emitting element is held at a relatively constant low temperature by the water cooling device, a decrease in irradiation intensity is suppressed.

  The optical fiber coating forming method according to the present invention is an optical fiber coating forming method in which an optical fiber coated with an ultraviolet curable resin is irradiated with ultraviolet rays to be cured. Is characterized by comprising a step of irradiating the ultraviolet curable resin with at least two types of ultraviolet rays having different peak wavelengths.

  As described above, the curing of the ultraviolet curable resin is promoted by irradiation with at least two types of ultraviolet rays having different peak wavelengths. At least two types of ultraviolet rays having different peak wavelengths are preferably irradiated simultaneously, but may be irradiated separately, and may be continuous light or pulsed light. In the case of pulsed light, it is possible to shift the ultraviolet irradiation timing of each pulse.

  According to this method, since the curing of the ultraviolet curable resin is promoted, a coating having a sufficient hardness can be formed, and the quality of the optical fiber can be improved. Further, since the semiconductor light emitting element is used, it is possible to form a coating of the optical fiber with a long life, low power consumption, and low running cost.

  In addition, at least two kinds of ultraviolet rays having different peak wavelengths emitted from the first and second semiconductor light emitting elements each have a wavelength range of ± 10 nm giving a peak value of an absorption spectrum of a photopolymerization initiator contained in the ultraviolet curable resin. Or within the range of the wavelength ± 10 nm giving the shoulder value of the absorption spectrum. That is, in this case, by irradiating the ultraviolet curable resin with at least two types of ultraviolet rays having different peak wavelengths, the photopolymerization initiator therein absorbs light, and the resin curing is promoted.

  In addition, as described above, it is preferable that the first and second semiconductor light emitting elements irradiate the ultraviolet curable resin with ultraviolet rays so as not to emit ultraviolet rays toward the light emitting surface of the semiconductor light emitting element other than itself. According to this arrangement, as described above, since the deterioration of the semiconductor light emitting element is avoided, the life of the semiconductor light emitting element can be extended.

  Further, as described above, it is preferable to irradiate the ultraviolet curable resin with ultraviolet rays while cooling the first and second semiconductor light emitting elements with a water cooling device. The cooling water removes heat from the semiconductor light emitting element, and the semiconductor light emitting element can be maintained at a relatively low constant temperature, so that the life of the semiconductor light emitting element can be extended. Moreover, since the semiconductor light emitting element is maintained at a relatively constant low temperature, a decrease in irradiation intensity is suppressed.

  According to the ultraviolet irradiation apparatus and the optical fiber coating forming method of the present invention, it is possible to form an optical fiber coating with a longer life, lower power consumption, and lower running cost than an ultraviolet irradiation apparatus using a UV lamp. it can.

  Hereinafter, the ultraviolet irradiation device and the optical fiber coating forming method according to the embodiment will be described. In addition, the same code | symbol shall be used for the same element and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a longitudinal sectional view of the ultraviolet irradiation device UVA along the traveling direction of the optical fiber during drawing, and FIG. 2 is a horizontal sectional view of the ultraviolet irradiation device UVA shown in FIG. FIG. 1 shows a cross-sectional view of the device cut along the arrow line II in FIG.

First, an optical fiber manufactured by the manufacturing method according to the present embodiment will be described.
In this embodiment, the optical fiber is configured to include a bare optical fiber F1 and coating layers C1 and C2 covering the surface thereof. The bare optical fiber F1 is a glass fiber formed by drawing a preform. The coating layers C1 and C2 are made of an ultraviolet curable resin that is cured when irradiated with ultraviolet rays, and have a function of protecting the surface of the bare optical fiber F1. The covering layers C1 and C2 are composed of two layers: an inner layer (primary resin) C1 adjacent to the bare optical fiber and an outer layer (secondary resin) C2 surrounding the inner layer C1.

  In the present embodiment, when the coating layers C1 and C2 are colored with a pigment / dye or the like, the coating layers C1 and C2 may have a function of imparting distinguishability. In addition, a colored layer made of an ultraviolet curable resin may be provided outside the coating layer C2.

An example of the radical photopolymerization initiator that can be included in the inner layer C1 and the outer layer C2 is as follows, and these photopolymerization initiators can be used either alone or in combination.
(1) Irgacure 907: (2-Methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one)
(2) Irgacure 819: (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide)

  The chemical structural formula of each photopolymerization initiator is shown in FIG. 11 (Irgacure 907: hereinafter, I-907) and FIG. 12 (Irgacure 819: hereinafter, I-819), respectively. “Irgacure” is a registered trademark, and the photopolymerization initiator is manufactured by Ciba Specialty Chemicals.

  An example of the resin material contained in the inner layer C1 and the outer layer C2 together with the above-described radical photopolymerization initiator is as follows.

(Inner layer C1)
For the inner layer C1, it is desirable to use a soft (referred to that having a Young's modulus of 1 kg / mm ² or less) ultraviolet curable resin. The inner layer resin is preferably a polyether-based or polyester-based urethane acrylate, and may contain a reactive dilution monomer as required.
Examples of the reactive dilution monomer include compounds such as N-vinylpyrrolidone and N-vinylcaprolactam, and these may be used alone or in combination of two or more. The Young's modulus of the inner layer C1 is adjusted by, for example, the molecular weight of the polyether portion of the ultraviolet curable resin and the type of the diluted monomer. That is, the inner layer C1 can reduce the Young's modulus by increasing the molecular weight of the polyether portion or by selecting a linear monofunctional diluent monomer having a large linear molecular weight.

(Outer layer C2)
For the outer layer C2, it is desirable to use a hard (referred to that having a Young's modulus of 10 kg / mm ² or more) ultraviolet curable resin. The outer layer resin is preferably a polyether-based or polyester-based urethane acrylate, and may contain a reactive dilution monomer as required. Examples of the reactive dilution monomer include compounds such as N-vinylpyrrolidone and N-vinylcaprolactam, and these may be used alone or in combination of two or more. The outer layer C2 can increase the Young's modulus by reducing the molecular weight of the polyester or polyether part, increasing the urethane group concentration, or selecting a monomer or polyfunctional monomer having a rigid molecular structure such as a benzene ring. I can do it.

  Referring to FIG. 1, the ultraviolet irradiation device UVA includes a transparent tube 31, an ultraviolet light source composed of a plurality of semiconductor light emitting elements 35, a condenser lens 34, a water cooling device 32, and a housing 33 that accommodates these. The casing 33 has a cylindrical shape, and a mount base 36 for fixing the semiconductor light emitting element 35 is fixed to the inner wall of the casing. The transparent tube 31 is arranged so that its longitudinal direction coincides with the traveling direction of the optical fiber F1. Then, the optical fiber F1 coated with two kinds of resins as the inner layer C1 and the outer layer C2 moves along the central axis of the transparent tube 31.

The transparent tube 31 is not particularly limited as long as it has translucency with respect to ultraviolet rays. For example, a quartz tube is preferably used. For cooling the transparent tube 31, an inert gas in a transparent tube 31 is introduced as shown by arrow G _IN, through the transparent tube 31, it is exhausted from the transparent tube 31 as indicated by arrow G _OUT The As this inert gas, for example, nitrogen gas is used at a low cost.

  In addition, when an inert gas is introduced into the transparent tube 31, the following secondary effects are also produced. First, when an inert gas is introduced into the transparent tube 31, the oxygen inside is expelled and the curing of the resin surface is promoted. The resin whose curing is inhibited by oxygen is a radical polymerization resin containing a photopolymerization initiator such as acylphosphine oxide or titanocene. Next, by flowing an inert gas such as nitrogen through the transparent tube 31, volatile components of the resin can be removed, so that the inner surface of the transparent tube 31 can be prevented from being fogged. That is, when the resin is irradiated with ultraviolet rays, the low molecular weight component of the resin is volatilized by the heat of curing reaction and radiant heat, and the volatile component adheres to the inner surface of the transparent tube 31 and cures. Although it tends to be blocked, in this embodiment, volatile components can be removed by an inert gas. Furthermore, the vibration of the optical fiber in the transparent tube 31 can be suppressed by bringing the flow of the inert gas closer to the laminar flow.

At the end of the coating apparatus is located in the drawing the upper side of the transparent tube 31, a gas inlet for introducing inert gas in the direction of arrow G _IN is formed. A gas introduction pipe INA is connected to the gas introduction port, and an inert gas is introduced into the transparent pipe 31 via the gas introduction pipe INA. Further, a gas discharge port is formed at the end of the transparent tube 31 opposite to the end to which the gas introduction pipe INA is connected. A gas discharge pipe OUTA is connected to the gas discharge port, and the inert gas and the component of the volatilized resin are discharged through the gas discharge pipe OUTA.

As the semiconductor light emitting element 35 constituting the ultraviolet light source, an ultraviolet laser diode (UV-LD) or an ultraviolet light emitting diode (UV-LED) is used. The semiconductor light emitting element 35 may be electrically connected to a control device (not shown), for example, and the power supplied to the semiconductor light emitting element 35 may be controlled by the control device. A condensing lens 34 is fixed on the front surface of the semiconductor light emitting element 35, and is preferably condensed into a line beam shape having a spot diameter of about 1 mm or about 1 mm wide × 12 mm long on a two-layer resin coating. In order to cure the ultraviolet curable resin, it is preferable that the irradiation intensity of the irradiated ultraviolet light is 5000 to 7000 mW / cm ² .

  The semiconductor light emitting element 35 has a considerably high temperature (˜100 ° C.) due to its own heat generation, the irradiation intensity is reduced due to the high temperature deterioration, and the life of the semiconductor light emitting element 35 is greatly reduced. In order to prevent this, the semiconductor light emitting element 35 is thermally connected to the water cooling device 32 via a mounting base 36 to which the semiconductor light emitting element 35 is fixed. The cooling device 32 is composed of a double metal cylinder, cooling water flows through a gap between these metal cylinders, and the inner metal cylinder is in contact with the mounting base 36. Cu and Al are listed as metals that can be used for the cooling device 32 and the base 36. The cooling water flowing in the cooling device 32 can remove the heat generated in the semiconductor light emitting element 35 through the mounting base 36 and keep the temperature of the semiconductor light emitting element 35 at about 40 ° C. Thereby, the life of the semiconductor light emitting element 35 is also extended.

The coating apparatus of the ultraviolet irradiation device UVA housing 33, the cooling water inlet port for introducing as shown cooling water by the arrow W _IN is formed. A cooling water introduction pipe INW is connected to the cooling water introduction port, and the base 36 of the semiconductor light emitting element 35 is cooled via the cooling water introduction pipe INW. Further, a cooling water discharge port is formed at the end of the casing 33 opposite to the end to which the cooling water introduction pipe INW is connected. A cooling water discharge pipe OUTW is connected to the cooling water discharge port, and the cooling water is discharged through the cooling water discharge pipe OUTW as indicated by an arrow W _OUT . The flow of cooling water may be reversed.

  The UV-LED that is the semiconductor light emitting element 35 has a single and narrow (± 5 nm) emission wavelength, but the wavelength (center wavelength) that gives the peak value of the emission spectrum is different in the ultraviolet irradiation device UVA of this system. More than one type of semiconductor light emitting elements 35 are simultaneously mounted on one ultraviolet irradiation device UVA. For example, the emission spectrum of the odd-numbered semiconductor light-emitting element 35 from the top of the drawing is the first emission spectrum (first semiconductor light-emitting element), and the emission spectrum of the even-numbered semiconductor light-emitting element 35 is the second emission spectrum. Yes (second semiconductor light emitting device). When a plurality of ultraviolet irradiation devices UVA are arranged along the traveling direction of the optical fiber, the first ultraviolet light irradiation device UVA includes the first semiconductor light emitting element 35 and the second ultraviolet irradiation device UVA. In addition, the second semiconductor light emitting element 35 may be mounted.

More specifically, the wavelengths λ1 and λ2 that give the peak values of the first and second spectra are ranges of wavelengths λ3 ± 10 nm that give the peak value of the absorption spectrum of the photopolymerization initiator contained in the ultraviolet curable resin, respectively. Or within the range of the wavelength λ4 ± 10 nm giving the shoulder value of the absorption spectrum. That is, they have the following relational expression.
・ Λ3-10nm ≦ λ1 ≦ λ3 + 10nm
・ Λ3-10nm ≦ λ2 ≦ λ3 + 10nm
・ Λ4-10nm ≦ λ1 ≦ λ4 + 10nm
・ Λ4-10nm ≦ λ2 ≦ λ4 + 10nm

  FIG. 9 is a table showing the types of photopolymerization initiators, the wavelength λ3 giving a peak value, and the wavelength λ4 giving a shoulder value.

  Practically, when an LED having a peak wavelength longer than 365 nm is used, the light emission output is increased.

  For example, when I-819 is used as the photopolymerization initiator in the resin, the peak position λ3 of the absorption wavelength is 280 to 300 nm, and the shoulder position λ4 is 365 nm. Two types of UV-LEDs having emission wavelength peak positions λ1 and λ2 in the range of 290 ± 10 nm and (B) 365 ± 10 nm may be used.

Such a UV-LED can be composed of the following materials.
(A) 290 nm ± 10 nm
Active layer: InAlGaN, InGaN, AlGaN, GaN, C, etc. Substrate: Al ₂ O ₃ , GaN, SiC, Si, etc. (B) 365 nm ± 10 nm
Active layer: InAlGaN, InGaN, AlGaN, GaN, C, etc. Substrate: Al ₂ O ₃ , GaN, SiC, Si, etc.

  When the photopolymerization initiator I-819 is used in the resin of the inner layer C1 and the outer layer C2, the center wavelengths λ1 and λ2 are (C) 365 ± 5 nm and (D) 395 ± 5 nm, respectively. LEDs may be used.

Such a UV-LED can be composed of the following materials.
(C) 365 nm ± 5 nm
Active layer: InAlGaN, InGaN, AlGaN, GaN, C, etc. Substrate: Al ₂ O ₃ , GaN, SiC, Si, etc. (D) 395 nm ± 5 nm
Active layer: InAlGaN, InGaN, AlGaN, GaN, C, etc. Substrate: Al ₂ O ₃ , GaN, SiC, Si, etc.

  As described above, since the width of the wavelength emitted from one LED is narrow, the use of one type of LED results in insufficient resin curability, but two or more types of LEDs are used to cure the UV curable resin. When the light having a wavelength with a certain width near the absorption peak wavelength is irradiated, the ultraviolet curable resin can be sufficiently cured.

  A plurality of semiconductor light emitting elements 35 are arranged around an optical fiber coated with resin. Since the light is condensed into a line beam shape with a spot diameter of about 1 mm or about 1 mm wide × 12 mm long on the outer layer C2, it is necessary to irradiate ultraviolet rays from a plurality of points in the circumferential direction in order to irradiate the entire circumference of the optical fiber. is there. For example, in the example shown in FIG. 1, three semiconductor light emitting elements 35 are arranged in one horizontal plane. The horizontal plane is perpendicular to the traveling direction of the optical fiber. These three light sources are set as one set, and several sets of light sources are arranged side by side along the traveling direction of the optical fiber in one ultraviolet irradiation device UVA.

  Although five sets of light sources are depicted in FIG. 1, the number of sets is determined by the total amount of ultraviolet energy to be irradiated. It is not necessarily 5 sets. A larger number of sets or a smaller number of sets may be arranged. When two or more types of ultraviolet light sources are simultaneously mounted on one ultraviolet irradiation device, ultraviolet light sources having different emission wavelength peak positions can be alternately arranged for each set.

  When the ultraviolet light UV hits the semiconductor light emitting element 35 on the opposite side, the temperature of the semiconductor light emitting element 35 rises or unnecessary oscillation occurs, so that the irradiation amount is reduced and the life is shortened. Therefore, as illustrated in FIG. 2, the semiconductor light emitting element 35 is arranged so that the semiconductor light emitting element 35 is not positioned on the opposite side across the optical fiber. For example, as shown in FIG. 2, the semiconductor light emitting elements 35 are arranged at intervals of 120 ° in one horizontal plane. That is, the emission direction of the ultraviolet rays UV forms an angle of 120 degrees in the horizontal plane. In other words, the first, second, and third semiconductor light emitting elements 35 in one horizontal plane are arranged so as not to emit ultraviolet rays toward the light emitting surface of the semiconductor light emitting element 35 other than itself.

  FIG. 3 is an exploded perspective view of the light source.

The mount base 36 made of rectangular ceramics has a mortar-shaped recess, and the semiconductor light emitting element 35 is fixed on the bottom surface of the recess. On the semiconductor light emitting element 35, a condensing lens 34 having a concave portion for accommodating the semiconductor light emitting element 35 is provided, and the condensing lens 34 is fitted in the concave portion of the mount base 36. A reflective film made of Ag, Al, or the like is preferably formed on the inner surface of the recess of the mount base 36 as necessary.
(Second Embodiment)

  4 is a longitudinal sectional view of the ultraviolet irradiation device UVA along the traveling direction of the optical fiber at the time of drawing, and FIG. 5 is a horizontal sectional view of the ultraviolet irradiation device UVA shown in FIG. 4 shows a cross-sectional view of the device taken along the line IV-IV in FIG.

  The difference between the device according to this embodiment and the device according to the first embodiment is only the arrangement of the semiconductor light emitting element 35. In the example shown in FIG. 5, four semiconductor light emitting elements 35 are arranged in one horizontal plane. These four light sources are set as one set, and several sets of light sources are arranged side by side along the traveling direction of the optical fiber in one ultraviolet irradiation device UVA.

  In FIG. 4, five sets of light sources are depicted, but the number of sets is determined by the total amount of ultraviolet energy irradiated. It is not necessarily 5 sets. A larger number of sets or a smaller number of sets may be arranged. When two or more types of ultraviolet light sources are simultaneously mounted on one ultraviolet irradiation device, ultraviolet light sources having different emission wavelength peak positions can be alternately arranged for each set.

  When the ultraviolet light UV hits the semiconductor light emitting element 35 on the opposite side, the temperature of the semiconductor light emitting element 35 rises or unnecessary oscillation occurs, so that the irradiation amount is reduced and the life is shortened. Therefore, as shown in FIG. 4, the semiconductor light emitting element 35 is inclined with respect to the horizontal plane so that the ultraviolet light UV does not strike the semiconductor light emitting element 35 on the opposite side. In other words, as shown in FIG. 5, the first, second, third, and fourth semiconductor light emitting elements 35 in one horizontal plane are ultraviolet rays toward the light emitting surface of the semiconductor light emitting element 35 other than itself. It is arrange | positioned so that it may not radiate | emit.

  Next, an optical fiber manufacturing apparatus used in the present embodiment will be described with reference to FIGS. 6 or 7, reference numerals 6, 7, 10, 11, and 12 denote ultraviolet irradiation devices, and the ultraviolet irradiation device UVA shown in FIG. 1 is shown as a representative of these ultraviolet irradiation devices. Yes.

  FIG. 6 is a view showing a first manufacturing apparatus for manufacturing an optical fiber (tandem coating method).

  The manufacturing apparatus includes a drawing furnace 2 that accommodates the preform 1, a forced cooling device 3, an outer diameter measuring device 4, a first coating device 5, ultraviolet irradiation devices 6 and 7, an outer diameter measuring device 8, a second The coating device 9, the ultraviolet irradiation devices 10, 11 and 12, the outer diameter measuring device 13, the bubble sensor 14, the guide roller 15, the capstan 16, and the take-up bobbin 17 are provided in order along the optical fiber passage path.

  FIG. 7 is a diagram showing a second manufacturing apparatus for manufacturing an optical fiber (dual coating method).

  This manufacturing apparatus includes a drawing furnace 2 that accommodates the preform 1, a forced cooling device 3, an outer diameter measuring device 4, a first coating device 5, a second coating device 9, an uneven thickness measuring device 20, and an ultraviolet irradiation device. 6, 7, 10, 11, an outer diameter measuring device 13, a bubble sensor 14, a guide roller 15, a capstan 16, and a take-up bobbin 17 are provided in order along the optical fiber passage path.

  In the manufacturing apparatus described above, the traveling direction of the optical fiber F drawn from the preform 1 is set to the vertical direction. The drawing furnace 2 is an apparatus for drawing a preform 1 mainly composed of quartz glass to form a bare optical fiber F1 (optical fiber F). The drawing furnace 2 has a heater arranged with (or enclosing) the preform 1 set in the drawing furnace 2. An end of the preform 1 is heated and melted by a heater, and is drawn to form an optical fiber F. The drawn optical fiber F moves along a predetermined traveling direction.

  The forced cooling device 3 is a device for cooling the drawn optical fiber F. The forced cooling device 3 has a predetermined length along a predetermined traveling direction in order to sufficiently cool the optical fiber F. In order to cool the optical fiber F, the forced cooling device 3 includes, for example, an intake port and an exhaust port (not shown), and cools the optical fiber F by introducing a cooling gas from the intake port and the exhaust port.

  The coating devices 5 and 9 are devices for applying a resin to the bare optical fiber. The coating devices 5 and 9 hold two types of liquid resins that are cured by ultraviolet rays, and the inner optical resin (primary resin 5A) is formed on the surface of the bare optical fiber by passing the bare optical fiber through the resin of the coating device. The outer layer resin (secondary resin 9A) is applied.

  In the example shown in FIG. 6, these resins are applied at different times and then sequentially cured (tandem coating), and in the example shown in FIG. 7, these resins are simultaneously applied and then simultaneously cured (dual coating). However, in the case of the tandem coating method, the space efficiency is worse than that in the dual coating method.

  The ultraviolet irradiation devices 6, 7, 10, 11, and 12 are devices for irradiating and curing two types of resins applied to the surface of the bare optical fiber by applying ultraviolet rays. A bare optical fiber having two types of resins coated on the surface passes through an ultraviolet irradiation device, whereby an optical fiber having a bare optical fiber and two coating layers is formed.

  The guide roller 15 is a device for guiding the optical fiber so that the optical fiber coated with two types of resins moves along a predetermined traveling direction. The optical fiber taken up by the capstan 16 is sent to the take-up bobbin 17 with the traveling direction changed by the guide roller 15. The winding bobbin 17 is a device for winding the completed optical fiber.

  In the above-described configuration, it is possible to provide sufficient curing characteristics from the surface layer portion to the inside of the resin coating, and it is possible to keep the fiber quality favorable. In particular, ultraviolet rays on the short wavelength side accelerate the curing of the resin surface. For example, when the photopolymerization initiator is I-819, when each semiconductor light emitting element is irradiated with ultraviolet light having a peak in the range of 280 to 300 nm, the surface of the ultraviolet curable resin is first cured. First, the surface is cured, and thereafter, with another ultraviolet irradiation device, for example, ultraviolet rays having a peak within a range of 365 ± 10 nm are irradiated from each semiconductor light emitting element to cure the inside of the ultraviolet curable resin. it can.

  If the surface of the resin is hardened, the direction of travel of the optical fiber can be changed by the guide roller. Therefore, the ultraviolet irradiation device that irradiates ultraviolet rays later is arranged in the vertical direction in FIG. 6 or FIG. Part of the devices 10, 11, (12) can be arranged downstream of the guide roller 15 and immediately before the capstan 16. For example, in the case of the tandem coat type system shown in FIG. 6, if a part of the ultraviolet irradiation devices 10, 11 and 12 is installed downstream of the guide roller 15, the space for that is used to cool the optical fiber, for example, by extending the cooling device. By extending the cooling length, the linear velocity of the optical fiber can be increased.

  Further, any number of ultraviolet irradiation devices may be used depending on the cured state of the resin coating layer of the optical fiber. 6 and 7 show examples of drawing an optical fiber. However, when an optical fiber wound around a bobbin is drawn out and further coated with an ultraviolet curable resin, ultraviolet rays are irradiated. The UV curable resin can be cured in the same manner.

  In addition, as described above, the optical fiber coating forming method according to the embodiment is an ultraviolet curable type optical fiber coating forming method in which an optical fiber coated with an ultraviolet curable resin is irradiated with ultraviolet rays to be cured. And a step of irradiating the resin with at least two types of ultraviolet rays having different peak wavelengths, and curing of the ultraviolet curable resin is promoted. Two types of ultraviolet rays having different peak wavelengths are preferably irradiated simultaneously, but may be irradiated separately, and may be continuous light or pulsed light. In the case of pulsed light, it is possible to shift the ultraviolet irradiation timing of each pulse.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples unless it exceeds the gist.

  A two-layer coated optical fiber was manufactured by a dual coating method drawing method using the ultraviolet irradiation device of FIG. The obtained double-layer coated optical fiber was coated and cured with a two-layer ultraviolet curable resin having an inner layer of 200 μmφ and an outer layer of 240 μmφ on the outer periphery of a glass fiber having an outer diameter of 125 μmφ.

  The photopolymerization initiator contained in the inner layer resin was one kind of I-819, and the photopolymerization initiator contained in the outer layer resin was also one kind of I-819. The combination of these coating resins was cured using one or two ultraviolet light emitting diodes (UV-LEDs) in one ultraviolet irradiation device as an ultraviolet light source. Nitrogen gas was used as an inert gas for cooling introduced into the transparent tube. The curability at that time was evaluated by the surface friction force. As materials for the inner layer and outer layer resins, urethane acrylate was used.

  Here, a method for measuring the surface friction force will be described.

  FIG. 8 is a schematic diagram showing a surface friction force measurement process. First, a part of the optical fiber F manufactured by the manufacturing apparatus shown in FIG. 7 is wound 100 times densely on a cylindrical rod 100 having a diameter of 6 mm to form a fiber group FB. The other part (length: about 1000 mm) of the optical fiber F is applied to the rod 100 and the pulley 101 around which the optical fiber F is wound. At this time, the pulley 101 and the rod 100 are arranged so that the optical fiber between them is substantially horizontal. A load cell 102 is attached to one end of the optical fiber hung on the pulley 101 and the rod 100, and a weight 103 of about 3.4 g is attached to the other end. In a state where the weight 103 is attached and balanced, the load related to the load cell 102 is set to zero as a reference value. Next, 500 mm / min. The load cell 102 is pulled up 200 mm along the arrow M at the speed of (the weight is also lifted at this time).

  At this time, the load measured by the load cell 102 is acquired at intervals of 0.02 seconds. The data acquired while the load cell 102 moves from 20 mm to 120 mm is divided into 10 sections for every 10 mm of travel distance of the load cell 102, and the surface frictional force of the coating layer, in other words, averages the maximum value of these sections. For example, the surface frictional force of the optical fiber. When this value is larger than 0.4N, the resin (surface) tends to be uncured, and it may be difficult to manufacture a good optical fiber. If the surface friction force is greater than 0.4 N, the optical fibers may stick to each other while being wound around the bobbin, and the optical fiber may not be drawn out from the bobbin. There is no such problem below 0.4N. In the case where it is smaller than 0.2N, since the resin is irradiated with ultraviolet rays more than necessary, the quartz tube tends to be clouded. These results are shown in FIG.

  As is apparent from the table shown in FIG. 10, two or more types having a peak position of the absorption wavelength of the photopolymerization initiator contained in the inner layer and outer layer resins, or a peak position of the emission wavelength falling within a range of ± 10 nm before and after the shoulder position. When the ultraviolet light source was employed (Examples 1 and 2), a preferable surface frictional force of 0.2 to 0.3 N was obtained. On the other hand, when one kind of ultraviolet light source having the peak position of the absorption wavelength of the photopolymerization initiator or the peak position of the emission wavelength falling within the range of the shoulder position ± 10 nm is employed (Comparative Example 1), the surface friction force is 0. 6N. Further, when an ultraviolet light source having a peak position of the absorption wavelength of the photopolymerization initiator or a peak position of the emission wavelength that does not fall within the range of the shoulder position ± 10 nm is employed (Comparative Example 2 and Comparative Example 3), the surface friction force is 1 .0N exceeded.

  In addition, the temperature of the ultraviolet light source is cooled from 100 ° C. or more to about 40 ° C. because the LEDs are arranged at intervals of 120 ° in the circumferential direction of the optical fiber so that the LEDs do not face each other, and there is a water cooling device. It was possible to prevent deterioration and suppress a decrease in irradiation intensity (a decrease in life). That is, when a light source such as UV-LD or UV-LED is sealed in a resin member, the light source itself becomes high temperature, so that the resin member or cavity sealing the light source deteriorates, and UV light The irradiation intensity to the optical fiber coating resin is lowered, and thus the photocurability of the UV photocurable resin is lowered. However, by adopting the cooling structure, the lifetime of the UV-LED itself due to this high temperature is reduced. The decrease can be suppressed. In particular, in this embodiment, since the plurality of UV-LEDs irradiate the ultraviolet curable resin with ultraviolet rays so as not to emit ultraviolet rays toward the light emitting surface of the semiconductor light emitting element other than itself, the temperature rises. Etc. are suppressed.

  In the above embodiment, a case where an ultraviolet light emitting diode having a plurality of emission wavelength peaks is mounted on one ultraviolet irradiation device is described. However, an ultraviolet light emitting diode having a different emission wavelength peak is mounted on each ultraviolet irradiation device. You can also. Moreover, it is also possible to use UV-LD instead of UV-LED. Also, the above-described embodiment can be applied when a resin is further coated on the coated optical fiber. Furthermore, the above embodiment can also be applied to resin coating when optical fibers are bundled into a tape. As described above, the optical fiber is not limited to a strand, and includes various types of optical fibers such as an overcoated optical fiber core and a resin-coated optical fiber. The above-described apparatus can also be applied to the case where the once wound optical fiber is drawn out again to perform resin coating.

It is a longitudinal cross-sectional view of the ultraviolet irradiation device UVA along the traveling direction of the optical fiber at the time of drawing. It is the II-II arrow horizontal sectional view of the ultraviolet irradiation device UVA shown in FIG. It is a disassembled perspective view of a light source. It is a longitudinal cross-sectional view of the ultraviolet irradiation device UVA along the traveling direction of the optical fiber at the time of drawing. FIG. 5 is a horizontal cross-sectional view of the UV irradiation apparatus UVA shown in FIG. FIG. 6 is a diagram showing a first manufacturing apparatus for manufacturing an optical fiber. FIG. 7 is a view showing a second manufacturing apparatus for manufacturing an optical fiber. FIG. 8 is a schematic diagram showing a surface friction force measurement process. It is a graph which shows the kind of photoinitiator, wavelength (lambda) 3 which gives a peak value, and wavelength (lambda) 4 which gives a shoulder value. It is a chart which shows an experimental result. It is a figure which shows a chemical structural formula. It is a figure which shows a chemical structural formula.

Explanation of symbols

  F1... Optical fiber, C1... Inner layer, C2... Outer layer, 35... Semiconductor light emitting element, 34.

Claims (7)

In an ultraviolet irradiation apparatus for irradiating an ultraviolet curable resin applied to a surface of an optical fiber with ultraviolet rays to cure the ultraviolet curable resin, at least a first position provided at a position where the ultraviolet curable resin can be irradiated with ultraviolet rays. 1 and a second semiconductor light emitting device,
The ultraviolet irradiation device, wherein the first and second semiconductor light emitting elements emit ultraviolet rays and have different peak wavelengths.   2. The ultraviolet irradiation apparatus according to claim 1, wherein the first and second semiconductor light emitting elements are arranged so as not to emit ultraviolet rays toward a light emitting surface of a semiconductor light emitting element other than the first and second semiconductor light emitting elements.   The ultraviolet irradiation device according to claim 1, wherein the first and second semiconductor light emitting elements are thermally connected to a water cooling device. In the optical fiber coating forming method of irradiating and curing an ultraviolet ray to an optical fiber coated with an ultraviolet curable resin,
The first and second semiconductor light emitting elements each include a step of irradiating the ultraviolet curable resin with ultraviolet rays having different peak wavelengths, respectively.   At least two types of ultraviolet rays having different peak wavelengths emitted from the first and second semiconductor light emitting elements each have a wavelength range of ± 10 nm that gives a peak value of an absorption spectrum of a photopolymerization initiator contained in the ultraviolet curable resin. 5. The method of forming an optical fiber coating according to claim 4, wherein the optical fiber coating is present within a wavelength range of ± 10 nm that gives a shoulder value of the absorption spectrum.   5. The ultraviolet curable resin is irradiated with ultraviolet rays so that the first and second semiconductor light emitting elements do not emit ultraviolet rays toward a light emitting surface of a semiconductor light emitting element other than itself. The optical fiber coating forming method according to claim 5.   The light according to any one of claims 4 to 6, wherein the ultraviolet curable resin is irradiated with ultraviolet rays while the first and second semiconductor light emitting elements are cooled by a water cooling device. Fiber coating formation method.

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